Abstract
The ionospheric Alfvén resonator (IAR) is a structure formed by the
rapid decrease in the plasma density above a planetary ionosphere. This
results in a corresponding increase in the Alfvén speed that can provide
partial reflection of Alfvén waves. At Earth, the IAR on auroral field
lines is associated with the broadband acceleration of auroral
particles, sometimes termed the Alfvenic aurora. This arises since phase
mixing in the IAR reduces the perpendicular wavelength of the Alfvén
waves, which enhances the parallel electric field due to electron
inertia. This parallel electric field fluctuates at frequencies of
0.1-20.0 Hz, comparable to the electron transit time through the region,
leading to the broadband acceleration. The prevalence of such broadband
acceleration at Jupiter suggests that a similar process can occur in the
Jovian IAR. A numerical model of Alfvén wave propagation in the Jovian
IAR has been developed to investigate these interactions. This model
describes the evolution of the electric and magnetic fields in the
low-altitude region close to Jupiter that is sampled during Juno’s
perijove passes. In particular, the model relates measurement of
magnetic fields below the ion cyclotron frequency from the MAG and Waves
instruments on Juno and electric fields from Waves to the associated
parallel electric fields that can accelerate auroral particles.